I. Introduction
A cell is the smallest unit in an organism. An organism is a living creature made up of one or more cells, such as bacteria or humans. Hence the fundamental components of all living things. Tissues are made up of several cells of the same kind that are interconnected and execute a common function; organs such as the stomach, heart, or brain are made up of multiple organs, and organ systems are made up of multiple organs (such as the digestive system, circulatory system, or nervous system).